Document EP 1 013 833 describes a hatch for accessing underground galleries and works provided with a frame and a lid, the lid being adapted to close an opening delimited by the frame.
The lid is hinged to the frame using a hinge that comprises a hinge pin 13 fixed to the frame and a groove 19 formed in the lid. The access hatch also has a heel 20 with a flat surface fixed to the frame and lugs 26 protruding from the lid. The lugs comprise a rounded cam surface that bears on the heel when the lid is opened (see column 5, lines 2 to 29 of EP 1 013 833).
The hinge pin 13 is fastened to the frame via tabs 12 welded to a plate, which in turn is fastened to the frame and the underground chamber by screws or bolts. Such a hinge is, however, fragile because under the force of the lid during repeated opening and closing operations, the screws or bolts for fastening the plate can loosen and cause poor positioning of the plate, and therefore of the hinge pin, thereby causing jamming and poor closing of the lid. Moreover, under the force of the lid during hinging, the tabs 12 supporting the hinge pin can fold, or even separate from the plate in the event of weld breaks, thereby again leading to a defective hinging.
Furthermore, the hinge in this document is costly and complicated to produce due to the many shaping and welding steps needed to develop the plate having the hinge pin.
Document FR 2 765 255 describes an access hatch comprising a frame and a plurality of lids. The lids can be moved from a closed position to an open position and are kept in a completely open position owing to a support piece cooperating with one edge of the lid.
This device does not allow positive guiding of the lid between its closed position and its open position and is also difficult to manufacture due to the large number of components.